Background and Objectives: Vitamin D is an essential secosteroid that plays a crucial role in the homeostasis of a few mineral elements, particularly calcium. Since vitamin D deficiency and thyroid diseases are two important global health problems, we aimed to investigate a possible relationship of vitamin D and calcium levels with hypothyroidism in an Iranian population.Methods: This case-control study was conducted on 175 subjects with hypothyroidism (75 males and 100 females) and 175 euthyroid controls (85 males and 90 females) who were referred to a laboratory in Gorgan, Iran. Serum levels of 25hydroxyvitamin D, calcium, thyroid-stimulating hormone (TSH), free triiodothyronine (free T3) and thyroxine (total T4) were measured in all participants.Results: Vitamin D and calcium were significantly lower in patients with hypothyroidism (P<0.0001). Free T3 and calcium levels differed significantly among hypothyroid patients based on their vitamin D status (P<0.0001), but vitamin D levels were within sufficient range in all groups. Moreover, there was a positive correlation between free T3 with vitamin D (r= 0.337, P<0.0001) and calcium (r= 0.361, P<0.0001) levels.Conclusions: Our results suggest that there may be a relationship between decreased vitamin D levels and thyroid function parameters.

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Introduction Oxidative stress known as a predictive marker for cardiovascular and metabolic diseases could be measured through pro‐oxidant antioxidant balance (PAB). The present study aimed to evaluate PAB and its association with high‐sensitivity C‐reactive protein (hs‐CRP) in the serum of postmenopausal women with diabetes mellitus. Methods In this case–control study, 99 diabetic and 100 healthy postmenopausal women without diabetes mellitus were recruited. Serum PAB values, hs‐CRP, lipid profile, insulin, and vitamin D levels were measured. Moreover, insulin resistance (HOMA‐IR, HOMA‐β and QUICKI), waist circumference (WC), waist‐to‐hip ratio (WHR), waist‐to‐height ratio (WHtR), and body mass index (BMI) were calculated. Results Serum PAB, hs‐CRP, insulin resistance, HOMA‐β, QUICKI, low‐density lipoprotein cholesterol (LDL‐C), high‐density lipoprotein cholesterol (HDL‐C), and triglycerides (TG) levels were significantly higher in the postmenopausal women with diabetes mellitus, while there was no significant difference in the total cholesterol (TC), serum insulin, WC, WHR, WHtR and vitamin D levels between the groups. Pearson correlation coefficient showed that HDL‐C and insulin levels were directly correlated with serum PAB. Also, there was a significant direct relationship between LDL‐C and insulin levels and hs‐CRP. There was no meaningful relationship between serum insulin and vitamin D levels and other assessed parameters. Backward logistic regression showed a positive relationship between diabetes mellitus and serum PAB and an inverse relationship with serum HDL levels. Conclusions Serum PAB, hs‐CRP concentration, and lipid profile were significantly different between postmenopausal women with and without diabetes mellitus. These differences may contribute to the development of coronary complications.